`h3` was too big but it can be the same size of `p` nor `h2`.
Fix doctring code block syntax.
Allow the `conf-log` role to link to the logging documentation.
Updated logging documentation on a common place.

* All logging information now resides on it's own document where all the currently documented features are explained.
* The master and minion logging configuration sections are now minimal and direct each option to the right place on the logging doc.
* A link to the logging doc was also added to the configuration document topic to help debugging issues when troubles are found.
* Headers fixed in the minion and master configuration docs